全文获取类型
收费全文 | 150篇 |
免费 | 7篇 |
国内免费 | 15篇 |
专业分类
化学 | 109篇 |
晶体学 | 5篇 |
力学 | 1篇 |
综合类 | 1篇 |
物理学 | 56篇 |
出版年
2023年 | 3篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 10篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 8篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有172条查询结果,搜索用时 15 毫秒
91.
Ferric stearate (FeSt) Langmuir-Blodgett (LB) films have been reacted chemically with H2S gas for making iron sulphide within the organic matrix. Films, before and after the reaction with H2S, have been analyzed with the X-ray reflectivity (XRR), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) studies. After sulphidation, more ‘pinhole’ defects form which changes the film morphology and the number of layers increases due to the rearrangement of the molecules. Formation of less ordered iron sulphide within the stearic acid multilayers after sulphidation increases the interfacial roughness that decreases the reflectivity. XPS analysis shows that polysulphide forms within the microenvironment of the FeSt LB films after reaction with H2S whereas both mono and polysulphide are produced when the reaction occurs with FeSt in bulk. 相似文献
92.
Oliver Ehlert Wendelin Bücking Jürgen Riegler Alexey Merkulov Thomas Nann 《Mikrochimica acta》2008,160(3):351-356
A novel and facile preparation method for colloidal ZnS nanoparticles doped with Mn2+ is introduced, using a simple one pot heating process followed by a capping procedure for saturation of the surface bound
doping atoms to increase the nanoparticles’ stability and photoluminescence quantum yield. The particles were transferred
into water with a standard ligand exchange method and investigated by means of laser Doppler electrophoresis, agarose gel
electrophoresis, and isotachophoresis.
Correspondence: Alexey Merkulov, Freiburg Materials Research Centre (FMF), University of Freiburg, Stefan-Meier-Strasse 21,
D-79104 Freiburg, Germany 相似文献
93.
In recent years multi-spectral imagery is steadily growing popularity. Multi-channel imaging which includes short-wave infrared (SWIR), mid-wave infrared (MWIR) and long-wave infrared (LWIR) systems are useful for threat detection, tracking, thermal signature detection and terrain analysis. In this paper, a broad band antireflection coating on ZnS substrate, simultaneously effective in SWIR, MWIR and LWIR is reported. The coating design approach was evolved using gradient index concept, where refractive index varies gradually from incident media to the ZnS (n = 2.2) substrate. The gradient index profile depicted by 4th degree polynomial n(t) = −0.45t4 + 1.9t3 − 2.7t2 + 1.9t + 1,where n(t) is the refractive index at the distance t from ambient, and t is the thickness in micron. The profile is best approximated by eight discrete step index layers, whose first layer is thorium fluoride (n = 1.42; lowest index stable material available). Other seven layers are replaced by two equivalent layer system of real materials thorium fluoride and zinc sulphide. Final 15 layers design is deposited by e-beam evaporation. The maximum layer thickness was restricted around 0.7 μm to overcome the stress problem in the film. This 15 layers coating has shown average transmission 95% in 0.9–10.5 μm spectral band having peak 99% at 9 μm. 相似文献
94.
Rajesh K Vatsa Chiranjib Majumder Onnattu D Jayakumar Shailendra K Kulshreshtha Jai P Mittal 《Journal of Chemical Sciences》2001,113(2):129-138
Multiphoton dissociation/ionization has been studied for CH3SCH3 at 355 and 532 nm using a time-of-flight mass spectrometer. The major ion signals observed at 355 nm are C+, CH3
+, HCS+, CH2S+, CH3S+ and CH3SCH3
+. Power dependence studies at 355 nm show a (2+1) REMPI process for the formation of parent ion. Peaks atm/e = 46, 47 and 61 show two-photon laser power dependence whereasm/e = 15 and 45 peaks show four-photon dependence. However, in 532 nm photo-ionisation, no parent ion signal is observed. A peak
atm/e = 35 corresponding to SH3
+ has been observed. SH3
+ has been suggested to originate from CH3SCH2
+ via a cyclic transition state. Photoionisation results of CH3SCH3 have been compared with those of CH3SSCH3, at these two wavelengths. 相似文献
95.
Resonant soft X-ray reflectivity measurements at and near the L3 absorption edge of sulphur have been performed on mechanically polished zinc sulphide using Indus-1 synchrotron source. A sulphur rich surface (∼15 nm thick) consisting of two layers with gradient electron density distribution was uniquely determined. As compared to bulk ZnS, the top layer has ∼30-50% less electron density whereas, the intermediate layer has ∼10-18% less electron density. Conventional hard X-ray reflectivity measurement at Cu Kα wavelength also indicates low electron density (sulphur rich) surface of ZnS but the technique was found insensitive for unique determination of electron density distribution. Optical constants of ZnS in the soft X-ray region (100-250 eV) have been reported for the first time and were in good agreement with the theoretically reported values. 相似文献
96.
《Analytical letters》2012,45(3):625-641
Abstract This paper describes a potentiometric method for the determination of sulphur in solid and liquid samples, using a sulphide ion selective electrode after the reduction distillation step. The determination of sulphide in solid and liquid samples without prior treatment was carried out by direct and titration potentiometric methods. The reproducibility of the method and the recovery of sulphate in solid samples was investigated using analytical reagent grade 99% sodium sulphate. Portions of aproximately 100 mg of reagent were subjected to the reduction distillation process. After the ion selective electrode showed a stable value of the potential, indicating that all the sulphate had been reduced to sulphide, the potentiometric titration with lead nitrate solution was performed. A mean recovery of 98% of sulphate was found. The potentiometric titration method described in this work, can be applied to determine S= in solid samples with the advantage that it does not require sample solubilization or extraction prior to the determination. The method yields an almost total reduction of sulphur and also a good precision. 相似文献
97.
《Analytical letters》2012,45(11):1987-2002
Abstract A procedure for study of the effects of the temperature on the response of ion-selective electrodes in which isothermal hysteresis cum determined at several concentrations are used for obtaining the temperature variation parameters (isothermal slope and potential coefficients and isopotential points) is proposed. The procedure was tested against the classic procedure in which calibration curves are obtained at different temperatures. 'All -solid-state' Ag2S and Ag2S/Agl electrodes with sensors applied to silver- and copper-loaded epoxy supports (and commercial electrodes, for comparison) were used for this purpose. The values of the temperature parameters obtained by the two procedures (in the raw 10–60°C) are compared. This comparison show that the present procedure yields acceptable values of temperature parameters for cases like the studied where the hysteresis is not very produced. 相似文献
98.
Ki-Hyun Kim 《International journal of environmental analytical chemistry》2013,93(11):805-817
In this study, the general requirements of the GC/PFPD analysis have been investigated in the measurements of reduced sulphur compounds (RSC) (hydrogen sulphide (H2S), methyl mercaptan (CH3SH), dimethylsulphide (DMS), and dimethyldisulphide (DMDS)) in air over a wide concentration range. To cover samples collected under various environmental conditions, a dual-mode analytical system was developed for both low (i.e. combination of a Peltier cooling (PC) and thermal desorption (TD) method) and high concentration detection settings (i.e. the direct loop injection (LI) method). They were combined to measure both lower- (ambient air samples in ppt level) and upper-bound concentrations (source-affected samples in ppb or ppm level) without the modulation of samples (e.g. dilution of samples). Their relative performance was evaluated in terms of differences in the analytical sensitivity by comparing both the calibration slope ratios and detection limits. According to this comparison, the result from the high mode setting exhibited a generally enhanced sensitivity relative to the low mode setting; such a difference can be explained in part in that the two analytical modes are calibrated under each respective set-up. Nonetheless, their relative detection characteristics were found to be highly consistent in various respects. The sensitivity of different S compounds tends to increase on the order of H2S, CH3SH, DMS, and DMDS (with two S atoms), regardless of the selected analytical mode. Based on the comparative analysis of the two GC settings, it is concluded that the versatile application of the GC/PFPD technique can be used effectively for the accurate quantification of S gases in various environmental samples. 相似文献
99.
The freezing point depression of cryolite (Na3AlF6) by the addition of Al2S3 and FeS was investigated. It was found that for contents of up to 10 wt.% Al2S3, it brings into the melt three new species. X-ray analysis of solidified melts of the system Na3AlF6–Al2S3 showed that it contained chiolite, Na5Al3F14 and Na2S. Chiolite originates from a reaction between Na3AlF6 and AlF3. This suggests that the system Na3AlF6–Al2S3 is a part of the reciprocal system NaF, AlF3//Na2S, Al2S3. The solubility of FeS in cryolite melt is so low that it cannot be determined by the thermal analysis. When FeO is added to the Na3AlF6–Al2S3 melt, Fe2+ cations and S2− anions react under the formation of solid FeS. A similar reaction was observed for Ni2+ and S2− ions. 相似文献
100.